pcretest man page

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pcretest was written as a test program for the PCRE regular expression
library itself, but it can also be used for experimenting with regular
expressions. This document describes the features of the test program; for
details of the regular expressions themselves, see the
pcrepattern
documentation. For details of the PCRE library function calls and their
options, see the
pcreapi
documentation.

-b
Behave as if each regex has the /B (show bytecode) modifier; the internal
form is output after compilation.

-C
Output the version number of the PCRE library, and all available information
about the optional features that are included, and then exit.

-d
Behave as if each regex has the /D (debug) modifier; the internal
form and information about the compiled pattern is output after compilation;
-d is equivalent to -b -i.

-dfa
Behave as if each data line contains the \D escape sequence; this causes the
alternative matching function, pcre_dfa_exec(), to be used instead of the
standard pcre_exec() function (more detail is given below).

-help
Output a brief summary these options and then exit.

-i
Behave as if each regex has the /I modifier; information about the
compiled pattern is given after compilation.

-m
Output the size of each compiled pattern after it has been compiled. This is
equivalent to adding /M to each regular expression. For compatibility
with earlier versions of pcretest, -s is a synonym for -m.

-oosize
Set the number of elements in the output vector that is used when calling
pcre_exec() or pcre_dfa_exec() to be osize. The default value
is 45, which is enough for 14 capturing subexpressions for pcre_exec() or
22 different matches for pcre_dfa_exec(). The vector size can be
changed for individual matching calls by including \O in the data line (see
below).

-p
Behave as if each regex has the /P modifier; the POSIX wrapper API is
used to call PCRE. None of the other options has any effect when -p is
set.

-q
Do not output the version number of pcretest at the start of execution.

-Ssize
On Unix-like systems, set the size of the runtime stack to size
megabytes.

-t
Run each compile, study, and match many times with a timer, and output
resulting time per compile or match (in milliseconds). Do not set -m with
-t, because you will then get the size output a zillion times, and the
timing will be distorted. You can control the number of iterations that are
used for timing by following -t with a number (as a separate item on the
command line). For example, "-t 1000" would iterate 1000 times. The default is
to iterate 500000 times.

-tm
This is like -t except that it times only the matching phase, not the
compile or study phases.

If pcretest is given two filename arguments, it reads from the first and
writes to the second. If it is given only one filename argument, it reads from
that file and writes to stdout. Otherwise, it reads from stdin and writes to
stdout, and prompts for each line of input, using "re>" to prompt for regular
expressions, and "data>" to prompt for data lines.

The program handles any number of sets of input on a single input file. Each
set starts with a regular expression, and continues with any number of data
lines to be matched against the pattern.

Each data line is matched separately and independently. If you want to do
multi-line matches, you have to use the \n escape sequence (or \r or \r\n,
etc., depending on the newline setting) in a single line of input to encode the
newline sequences. There is no limit on the length of data lines; the input
buffer is automatically extended if it is too small.

An empty line signals the end of the data lines, at which point a new regular
expression is read. The regular expressions are given enclosed in any
non-alphanumeric delimiters other than backslash, for example:

/(a|bc)x+yz/

White space before the initial delimiter is ignored. A regular expression may
be continued over several input lines, in which case the newline characters are
included within it. It is possible to include the delimiter within the pattern
by escaping it, for example

/abc\/def/

If you do so, the escape and the delimiter form part of the pattern, but since
delimiters are always non-alphanumeric, this does not affect its interpretation.
If the terminating delimiter is immediately followed by a backslash, for
example,

/abc/\

then a backslash is added to the end of the pattern. This is done to provide a
way of testing the error condition that arises if a pattern finishes with a
backslash, because

/abc\/

is interpreted as the first line of a pattern that starts with "abc/", causing
pcretest to read the next line as a continuation of the regular expression.
PATTERN MODIFIERS

A pattern may be followed by any number of modifiers, which are mostly single
characters. Following Perl usage, these are referred to below as, for example,
"the /i modifier", even though the delimiter of the pattern need not
always be a slash, and no slash is used when writing modifiers. Whitespace may
appear between the final pattern delimiter and the first modifier, and between
the modifiers themselves.

The /i, /m, /s, and /x modifiers set the PCRE_CASELESS,
PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
pcre_compile() is called. These four modifier letters have the same
effect as they do in Perl. For example:

/caseless/i

The following table shows additional modifiers for setting PCRE options that do
not correspond to anything in Perl:

Those specifying line ending sequencess are literal strings as shown. This
example sets multiline matching with CRLF as the line ending sequence:

/^abc/m<crlf>

Details of the meanings of these PCRE options are given in the
pcreapi
documentation.
Finding all matches in a string

Searching for all possible matches within each subject string can be requested
by the /g or /G modifier. After finding a match, PCRE is called
again to search the remainder of the subject string. The difference between
/g and /G is that the former uses the startoffset argument to
pcre_exec() to start searching at a new point within the entire string
(which is in effect what Perl does), whereas the latter passes over a shortened
substring. This makes a difference to the matching process if the pattern
begins with a lookbehind assertion (including \b or \B).

If any call to pcre_exec() in a /g or /G sequence matches an
empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
flags set in order to search for another, non-empty, match at the same point.
If this second match fails, the start offset is advanced by one, and the normal
match is retried. This imitates the way Perl handles such cases when using the
/g modifier or the split() function.

Other modifiers

There are yet more modifiers for controlling the way pcretest
operates.

The /+ modifier requests that as well as outputting the substring that
matched the entire pattern, pcretest should in addition output the remainder of
the subject string. This is useful for tests where the subject contains
multiple copies of the same substring.

The /B modifier is a debugging feature. It requests that pcretest
output a representation of the compiled byte code after compilation. Normally
this information contains length and offset values; however, if /Z is
also present, this data is replaced by spaces. This is a special feature for
use in the automatic test scripts; it ensures that the same output is generated
for different internal link sizes.

The /L modifier must be followed directly by the name of a locale, for
example,

/pattern/Lfr_FR

For this reason, it must be the last modifier. The given locale is set,
pcre_maketables() is called to build a set of character tables for the
locale, and this is then passed to pcre_compile() when compiling the
regular expression. Without an /L modifier, NULL is passed as the tables
pointer; that is, /L applies only to the expression on which it appears.

The /I modifier requests that pcretest output information about the
compiled pattern (whether it is anchored, has a fixed first character, and
so on). It does this by calling pcre_fullinfo() after compiling a
pattern. If the pattern is studied, the results of that are also output.

The /D modifier is a PCRE debugging feature, and is equivalent to
/BI, that is, both the \fP/B\fP and the /I modifiers.

The /F modifier causes pcretest to flip the byte order of the
fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
facility is for testing the feature in PCRE that allows it to execute patterns
that were compiled on a host with a different endianness. This feature is not
available when the POSIX interface to PCRE is being used, that is, when the
/P pattern modifier is specified. See also the section about saving and
reloading compiled patterns below.

The /S modifier causes pcre_study() to be called after the
expression has been compiled, and the results used when the expression is
matched.

The /M modifier causes the size of memory block used to hold the compiled
pattern to be output.

The /P modifier causes pcretest to call PCRE via the POSIX wrapper
API rather than its native API. When this is done, all other modifiers except
/i, /m, and /+ are ignored. REG_ICASE is set if /i is
present, and REG_NEWLINE is set if /m is present. The wrapper functions
force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.

The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8
option set. This turns on support for UTF-8 character handling in PCRE,
provided that it was compiled with this support enabled. This modifier also
causes any non-printing characters in output strings to be printed using the
\x{hh...} notation if they are valid UTF-8 sequences.

If the /? modifier is used with /8, it causes pcretest to
call pcre_compile() with the PCRE_NO_UTF8_CHECK option, to suppress the
checking of the string for UTF-8 validity.

Before each data line is passed to pcre_exec(), leading and trailing
whitespace is removed, and it is then scanned for \ escapes. Some of these are
pretty esoteric features, intended for checking out some of the more
complicated features of PCRE. If you are just testing "ordinary" regular
expressions, you probably don't need any of these. The following escapes are
recognized:

\a alarm (BEL, \x07)
\b backspace (\x08)
\e escape (\x27)
\f formfeed (\x0c)
\n newline (\x0a)
\qdd set the PCRE_MATCH_LIMIT limit to dd (any number of digits)
\r carriage return (\x0d)
\t tab (\x09)
\v vertical tab (\x0b)
\nnn octal character (up to 3 octal digits)
\xhh hexadecimal character (up to 2 hex digits)
\x{hh...} hexadecimal character, any number of digits in UTF-8 mode
\A pass the PCRE_ANCHORED option to pcre_exec() or pcre_dfa_exec()
\B pass the PCRE_NOTBOL option to pcre_exec() or pcre_dfa_exec()
\Cdd call pcre_copy_substring() for substring dd after a successful match (number less than 32)
\Cname call pcre_copy_named_substring() for substring "name" after a successful match (name termin-
ated by next non alphanumeric character)
\C+ show the current captured substrings at callout time
\C- do not supply a callout function
\C!n return 1 instead of 0 when callout number n is reached
\C!n!m return 1 instead of 0 when callout number n is reached for the nth time
\C*n pass the number n (may be negative) as callout data; this is used as the callout return value
\D use the pcre_dfa_exec() match function
\F only shortest match for pcre_dfa_exec()
\Gdd call pcre_get_substring() for substring dd after a successful match (number less than 32)
\Gname call pcre_get_named_substring() for substring "name" after a successful match (name termin-
ated by next non-alphanumeric character)
\L call pcre_get_substringlist() after a successful match
\M discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings
\N pass the PCRE_NOTEMPTY option to pcre_exec() or pcre_dfa_exec()
\Odd set the size of the output vector passed to pcre_exec() to dd (any number of digits)
\P pass the PCRE_PARTIAL option to pcre_exec() or pcre_dfa_exec()
\Qdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd (any number of digits)
\R pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
\S output details of memory get/free calls during matching
\Z pass the PCRE_NOTEOL option to pcre_exec() or pcre_dfa_exec()
\? pass the PCRE_NO_UTF8_CHECK option to pcre_exec() or pcre_dfa_exec()
\>dd start the match at offset dd (any number of digits);
this sets the startoffset argument for pcre_exec() or pcre_dfa_exec()
\<cr> pass the PCRE_NEWLINE_CR option to pcre_exec() or pcre_dfa_exec()
\<lf> pass the PCRE_NEWLINE_LF option to pcre_exec() or pcre_dfa_exec()
\<crlf> pass the PCRE_NEWLINE_CRLF option to pcre_exec() or pcre_dfa_exec()
\<any> pass the PCRE_NEWLINE_ANY option to pcre_exec() or pcre_dfa_exec()

The escapes that specify line ending sequences are literal strings, exactly as
shown. No more than one newline setting should be present in any data line.

A backslash followed by anything else just escapes the anything else. If
the very last character is a backslash, it is ignored. This gives a way of
passing an empty line as data, since a real empty line terminates the data
input.

If \M is present, pcretest calls pcre_exec() several times, with
different values in the match_limit and match_limit_recursion
fields of the pcre_extra data structure, until it finds the minimum
numbers for each parameter that allow pcre_exec() to complete. The
match_limit number is a measure of the amount of backtracking that takes
place, and checking it out can be instructive. For most simple matches, the
number is quite small, but for patterns with very large numbers of matching
possibilities, it can become large very quickly with increasing length of
subject string. The match_limit_recursion number is a measure of how much
stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
to complete the match attempt.

When \O is used, the value specified may be higher or lower than the size set
by the -O command line option (or defaulted to 45); \O applies only to
the call of pcre_exec() for the line in which it appears.

If the /P modifier was present on the pattern, causing the POSIX wrapper
API to be used, the only option-setting sequences that have any effect are \B
and \Z, causing REG_NOTBOL and REG_NOTEOL, respectively, to be passed to
regexec().

The use of \x{hh...} to represent UTF-8 characters is not dependent on the use
of the /8 modifier on the pattern. It is recognized always. There may be
any number of hexadecimal digits inside the braces. The result is from one to
six bytes, encoded according to the UTF-8 rules.

By default, pcretest uses the standard PCRE matching function,
pcre_exec() to match each data line. From release 6.0, PCRE supports an
alternative matching function, pcre_dfa_test(), which operates in a
different way, and has some restrictions. The differences between the two
functions are described in the
pcrematching
documentation.

If a data line contains the \D escape sequence, or if the command line
contains the -dfa option, the alternative matching function is called.
This function finds all possible matches at a given point. If, however, the \F
escape sequence is present in the data line, it stops after the first match is
found. This is always the shortest possible match.

This section describes the output when the normal matching function,
pcre_exec(), is being used.

When a match succeeds, pcretest outputs the list of captured substrings that
pcre_exec() returns, starting with number 0 for the string that matched
the whole pattern. Otherwise, it outputs "No match" or "Partial match"
when pcre_exec() returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PARTIAL,
respectively, and otherwise the PCRE negative error number. Here is an example
of an interactive pcretest run.

If the strings contain any non-printing characters, they are output as \0x
escapes, or as \x{...} escapes if the /8 modifier was present on the
pattern. See below for the definition of non-printing characters. If the
pattern has the /+ modifier, the output for substring 0 is followed by
the the rest of the subject string, identified by "0+" like this:

re> /cat/+
data> cataract
0: cat
0+ aract

If the pattern has the /g or /G modifier, the results of successive
matching attempts are output in sequence, like this:

If any of the sequences \C, \G, or \L are present in a
data line that is successfully matched, the substrings extracted by the
convenience functions are output with C, G, or L after the string number
instead of a colon. This is in addition to the normal full list. The string
length (that is, the return from the extraction function) is given in
parentheses after each string for \C and \G.

Note that whereas patterns can be continued over several lines (a plain ">"
prompt is used for continuations), data lines may not. However newlines can be
included in data by means of the \n escape (or \r, \r\n, etc., depending on
the newline sequence setting).

When the alternative matching function, pcre_dfa_exec(), is used (by
means of the \D escape sequence or the -dfa command line option), the
output consists of a list of all the matches that start at the first point in
the subject where there is at least one match. For example:

Since the matching function does not support substring capture, the escape
sequences that are concerned with captured substrings are not relevant.
RESTARTING AFTER A PARTIAL MATCH

When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
indicating that the subject partially matched the pattern, you can restart the
match with additional subject data by means of the \R escape sequence. For
example:

If the pattern contains any callout requests, pcretest's callout function
is called during matching. This works with both matching functions. By default,
the called function displays the callout number, the start and current
positions in the text at the callout time, and the next pattern item to be
tested. For example, the output

--->pqrabcdef
0 ^ ^ \d

indicates that callout number 0 occurred for a match attempt starting at the
fourth character of the subject string, when the pointer was at the seventh
character of the data, and when the next pattern item was \d. Just one
circumflex is output if the start and current positions are the same.

Callouts numbered 255 are assumed to be automatic callouts, inserted as a
result of the /C pattern modifier. In this case, instead of showing the
callout number, the offset in the pattern, preceded by a plus, is output. For
example:

When pcretest is outputting text in the compiled version of a pattern,
bytes other than 32-126 are always treated as non-printing characters are are
therefore shown as hex escapes.

When pcretest is outputting text that is a matched part of a subject
string, it behaves in the same way, unless a different locale has been set for
the pattern (using the /L modifier). In this case, the isprint()
function to distinguish printing and non-printing characters.

The facilities described in this section are not available when the POSIX
inteface to PCRE is being used, that is, when the /P pattern modifier is
specified.

When the POSIX interface is not in use, you can cause pcretest to write a
compiled pattern to a file, by following the modifiers with > and a file name.
For example:

/pattern/im >/some/file

See the
pcreprecompile
documentation for a discussion about saving and re-using compiled patterns.

The data that is written is binary. The first eight bytes are the length of the
compiled pattern data followed by the length of the optional study data, each
written as four bytes in big-endian order (most significant byte first). If
there is no study data (either the pattern was not studied, or studying did not
return any data), the second length is zero. The lengths are followed by an
exact copy of the compiled pattern. If there is additional study data, this
follows immediately after the compiled pattern. After writing the file,
pcretest expects to read a new pattern.

A saved pattern can be reloaded into pcretest by specifing < and a file
name instead of a pattern. The name of the file must not contain a < character,
as otherwise pcretest will interpret the line as a pattern delimited by <
characters.
For example:

re> </some/file
Compiled regex loaded from /some/file
No study data

When the pattern has been loaded, pcretest proceeds to read data lines in
the usual way.

You can copy a file written by pcretest to a different host and reload it
there, even if the new host has opposite endianness to the one on which the
pattern was compiled. For example, you can compile on an i86 machine and run on
a SPARC machine.

File names for saving and reloading can be absolute or relative, but note that
the shell facility of expanding a file name that starts with a tilde (~) is not
available.

The ability to save and reload files in pcretest is intended for testing
and experimentation. It is not intended for production use because only a
single pattern can be written to a file. Furthermore, there is no facility for
supplying custom character tables for use with a reloaded pattern. If the
original pattern was compiled with custom tables, an attempt to match a subject
string using a reloaded pattern is likely to cause pcretest to crash.
Finally, if you attempt to load a file that is not in the correct format, the
result is undefined.